They don't take me serious..

I'm writing to get a little advice from you lovely ladies! When it comes to dating I can never seem to get a guy that will take me serious.. they either turn out to be married or they are single but only want to fuck and don't wish to purse a relationship or after speaking to them for how long they decide to get serious with someone else? It breaks my heart.. I have met guys from all different kinds of places. I have acted like myself I have tried 'good' guys and 'bad. They don't do each other justice. Only one guy that loved me so dearly and I loved him so much was a murderer and lived for that so I had to leave him. Besides that what can this all be about? What should I do? I'm in no rush but it's just slowly starting to get to me and affect me